Mikolajewski D J, Rüsen L, Mauersberger R, Johansson F, Rolff J
Institut für Biologie, Freie Universität Berlin, Berlin, Germany.
Förderverein Feldberg-Uckermärkische Seenlandschaft e.V., Templin, Germany.
J Evol Biol. 2015 Jul;28(7):1354-63. doi: 10.1111/jeb.12658. Epub 2015 Jun 8.
Although changes in magnitude of single traits responding to selective agents have been studied intensively, little is known about selection shaping networks of traits and their patterns of covariation. However, this is central for our understanding of phenotypic evolution as traits are embedded in a multivariate environment with selection affecting a multitude of traits simultaneously rather than individually. Here, we investigate inter- and intraspecific patterns of trait integration (trait correlations) in the larval abdomen of dragonflies as a response to a change in predator selection. Species of the dragonfly genus Leucorrhinia underwent a larval habitat shift from predatory fish to predatory dragonfly-dominated lakes with an associated relaxation in selection pressure from fish predation. Our results indicate that the habitat-shift-induced relaxed selection pressure caused phenotypic integration of abdominal traits to be reduced. Intraspecific findings matched patterns comparing species from both habitats with higher abdominal integration in response to predatory fish. This higher integration is probably a result of faster burst swimming speed. The abdomen holds the necessary morphological machinery to successfully evade predatory fish via burst swimming. Hence, abdominal traits have to function in a tight coordinated manner, as maladaptive variation and consequently nonoptimal burst swimming would cause increased mortality. In predatory dragonfly-dominated lakes, no such strong link between burst swimming and mortality is present. Our findings highlight the importance of studying multivariate trait relationships as a response to selection for understanding patterns of phenotypic diversification.
尽管针对选择性因素做出反应的单一性状大小变化已得到深入研究，但对于塑造性状网络及其协变模式的选择作用却知之甚少。然而，这对于我们理解表型进化至关重要，因为性状处于多变量环境中，选择会同时影响众多性状而非单个性状。在此，我们研究蜻蜓幼虫腹部的种间和种内性状整合模式（性状相关性），作为对捕食者选择变化的一种反应。蜻蜓属Leucorrhinia的物种经历了幼虫栖息地从有捕食性鱼类的环境转变为以捕食性蜻蜓为主的湖泊，同时伴随着来自鱼类捕食的选择压力的缓解。我们的结果表明，栖息地转变引起的选择压力缓解导致腹部性状的表型整合降低。种内研究结果与比较来自两种栖息地的物种的模式相符，即对捕食性鱼类的反应是腹部整合程度更高。这种更高的整合可能是爆发式游泳速度更快的结果。腹部拥有通过爆发式游泳成功躲避捕食性鱼类所需的形态机制。因此，腹部性状必须紧密协调地发挥作用，因为适应不良的变异以及由此导致的非最优爆发式游泳会增加死亡率。在以捕食性蜻蜓为主的湖泊中，爆发式游泳与死亡率之间不存在如此紧密的联系。我们的研究结果凸显了研究多变量性状关系作为对选择的反应对于理解表型多样化模式的重要性。
